1. Field of the Invention
The present invention relates to video reproducing apparatus capable of reproducing video based on compressed video data (for example, MPEG data).
2. Description of the Prior Art
MPEG (Moving Picture Experts Group), which is the international standard of the compression/expansion of color motion pictures, has been rapidly spread and applied to computers, communications, entertainment, etc. Of MPEG, MPEG 1 is employed in storage media such as a CD-ROM and MPEG 2 is employed in storage media such as a DVD and also in digital broadcasting.
Now, referring to FIG. 5, the data arrangement structure (bit stream) of MPEG will be described. As shown in FIG. 5, the data arrangement structure of MPEG is formed in a hierarchy structure. The sequence 1 representing the entirety of one vide program is constituted by GOPs (Group of Picture) 2 each of which is an information block formed on a unit basis of a prescribed number of frames, and the GOP 2 is constituted by a prescribed number of pictures 3. Further, the picture 3 is constituted by plural slices 4 which are blocks formed by dividing the picture 2. The slice 4 is constituted by a plurality of macro blocks (hereinafter called as MBs) 5. The MB 5 is constituted by blocks 6 each formed by 8×8 pixels. The MB 5 is a minimum unit for coding of MPEG, that is, DCT (Discrete Cosine Transform) processing.
As shown in FIG. 6, GOP 2 includes an intra-coded picture (hereinafter called as an I picture) which is video information for intra-frame coding, a forward predictive-coded picture (hereinafter called as a P picture) which is video information for forward prediction coding, and a bidirectionally predictive-coded picture (hereinafter called as a B picture) which is video information for bidirectional prediction coding. As shown in FIG. 6, one GOP 2 is constituted by prescribed numbers of I, P and B pictures which are set in advance. In FIG. 6, as shown by the arrows, an I picture 7a and a P picture 7e are referenced by B pictures 7b, 7c, and 7d. Further, the I picture 7a is referenced by the P picture 7e. 
Further, compressed video data (MPEG data) before decoding is saved as coded data of the I picture with regard to the I picture, and as difference data between the P picture and the I picture referenced by the P picture or difference data between the B picture and the P picture. During the decoding, the P and B pictures are produced by using the coded data of the I picture and the difference data.
In the reproduction mode, the respective I, P and B pictures shown in FIG. 6 are sequentially reproduced. In this case, the compression rates of video information of these pictures differ from one another. In the still picture mode, when a picture stops at the B picture having the highest compression rate, the picture quality of this picture is quite degraded.
There is an apparatus for reproducing the pictures of video data, wherein when the reproduction of video is paused in a prescribed manner at a B picture, one of I pictures closest to the B picture is displayed in place of the B picture (see, for example, Japanese Unexamined Patent Publication No. 2000-308016). There is also an apparatus for reproducing pictures of the video data wherein, when the reproduction of video is paused in a prescribed manner, a picture having the best picture quality among the pictures including a stopped picture and nearby pictures is displayed (see, for example, Japanese Unexamined Patent Publication No. 10-257501).
However, according to the video reproducing apparatuses disclosed by Patent Documents 1 and 2, compressed video data is expanded (decoded) by pausing operation and still pictures based on the decoded video data are shown. Therefore, the picture quality of such a picture depends on a decoding function of the video reproducing apparatus. As a result, the picture quality of the still picture might be degraded.